In an infection setting, Th2 polarization has been reported in RSV-infected infants with acute bronchiolitis that showed an IL-4 skewed IL-4/IFN-γ ratio compared to infants with upper respiratory tract infection, indicating that increased Th2-type and/or decreased Th1-type responses may contribute to severe disease (25). This evidence concerns the gene IL4 and Recurrent upper respiratory tract infections.